Liquid crystal displays are widely applied in various electronic products as display member. More specifically, GOA (Gate Driver On Array, abbreviation: GOA) circuit is a critical component in liquid crystal display devices. A GOA circuit is one sort of technology using a conventional TFT array fabricate process to implement a gate scan driving signal circuit on array substrate, which realize the progressive scanning of gate driving.
Display panels based on Low Temperature Poly-silicon (abbreviation: LTPS) may be classified according to the types of Thin Film Transistor (abbreviation: TFT) adopted in panels into NMOS type, PMOS type, and CMOS type which comprises both NMOS and PMOS. Similarly, GOA circuit may be classified into NMOS circuit, PMOS circuit and CMOS circuit. NMOS circuit, in comparison with CMOS circuit, lacks PP (P doping, a.k.a. phosphorus ion doping) mask-fabricate process contributes to higher yield and lower cost significantly. A stable NMOS circuit is in industrially desired. In the situation of being out of power abnormally, if GOA circuit could not effectively realize ALL Gate On function (Setting all gate driving signals as valid voltage level, so as to execute liquid crystal display panel scanning simultaneously), the display panel would show sticking and flicker.
Take forward scanning for example, when there is out of power abnormally in GOA circuit unit illustrated in FIG. 1, the (n+1)-th clock signal feed in thin-film-transistor NT3 is in high voltage level. In this way, the forward scan control signal and (n+1)-th clock signal will be pulled down to low voltage level simultaneously causing the high voltage level of the gate of the thin-film-transistor NT5 may not be released further causing the thin-film-transistor NT5 kept conducting. Therefore, thin-film-transistor NT8 is also kept conducting. The high voltage signal VGH and the low voltage signal VGL may be in superposition with each other, thus, the gate of thin-film-transistor NT7 may not be pulled down completely causing the gate driving signal G(n) outputted by thin-film-transistor NT7 to thin-film-transistor of pixel units be pulled low. Therefore, the gate driving signal G(n) would be unable to open the thin-film-transistor of pixel units causing the charges of pixel electrode not be released in time. In the long run, the sticking and flicker would happen in the active area when the display panel is out of power abnormally.